It is a chilly July morning in the Pyrenees and a lone cyclist is pedalling laboriously up a snow-topped mountain followed by a woman driving a white Ford Transit.

Londoner Luke Bream, 33, sporting a pink and white jersey, is attacking a punishing mountain leg of the world's most famous cycle race, the Tour de France. It is clearly hard going.

"I'm looking at a horrendous mountain right in front of me and Luke is going up it," reports his team leader from her van. "This is really tough. It's also chilly."

The following day is worse, she says. "Now it's scorching hot and this stage is through the rolling countryside. It's all uphill and downhill and Luke tells me his legs feel absolutely dead."

At least he is well in front of the 152 remaining riders (189 set off from London) in the three-week long Tour. In fact, he is 24 hours ahead as he has been along the entire route so far.

Mr Bream, however, will not be sporting any yellow jersey for winning this or any other stage of the prestigious race. Nor will his team coordinator, cook, medic, mechanic and mental coach - his mother Carolyn, 68 - be up for international accolades or sponsorship windfalls.

In a week when a blood-doping scandal involving the pre-race favourite Alexandr Vinokourov cast a shadow over the Tour, the British enthusiast is setting an inspirational example to amateur cyclists.

"He doesn't have any sponsorship and we're doing it on a shoestring," Mrs Bream says, having stopped her van on the Col de la Pierre St Martin mountain pass in the Pyrenees to speak to the Guardian. "I reckon by the end of it we'll have spent, oooh let's see, £1,500, maybe a little more but £2,000 maximum."

According to Mrs Bream, a former primary school teacher, each day - apart from rest days - her son sets off at 8am after a breakfast of bread rolls, jam, honey and coffee.

"At the beginning we were leaving earlier but we were starting before the race officials put arrows along the route and ended up going the wrong way," she says. "Now we start half an hour before the arrow men. After 15km they overtake us with lots of hooting and waving and cheering and we don't go astray.

"He takes short breaks to eat and I cook pasta and chicken in sauces in the back of the van. It's usually around 4pm he wants hot food, which is difficult to find in France at that hour, so he eats McDonald's if there's one nearby."

Sleeping quarters are fairly basic. "We sleep in the van; me over the front three seats and him in the back with the bike. Luckily there's only one bike."

Mrs Bream says that after conquering the mountain stages Luke is optimistic about finishing his personal Tour de France. "Having come so far he now thinks he can beat it, that it won't be too bad."

And amid the backdrop of accusations of cheating among official Tour de France riders, she assures the Guardian Luke is on nothing but his own adrenaline.

"Oh no, Luke doesn't take drugs at the best of times, not even an aspirin if he has a headache. He does take some cod liver oil tablets, but apart from that he's doing this largely on Coca Cola and jam butties."

Many Britons have attempted one or more of the 20 stages of the 2007 Tour but the south London food wholesaler is believed to be the only one doing the entire route solo and cycling the entire 2,200 mile London to Paris route one day in advance of the race itself.

If he succeeds in reaching the final stretch along the cobblestones of the Champs Elysées this Sunday it will be a remarkable feat of physical and mental endurance. His determination and success, so far, is even more remarkable given that he only took up cycling a year ago.

A day behind, the official riders with their multimillion pound sponsorship deals are followed by a roadshow of team officials, mechanics, spare bikes and equipment. It is the sort of back-up Mr Bream can only dream of as he ploughs his solitary furrow up the mountain.

"We've got two spare tyres and five inner tubes," Mrs Bream admits. "Luckily we've only had one puncture so far."

"It's a personal challenge. What he's discovered is that it's not about physical fitness but about being strong mentally."

In an unsuccessful internet appeal for what he called "like-minded lunatics" to join him, Mr Bream wrote: "We will be camping/living in the van. It will be basic, cheap and cheerful adventure." He added: "I have loads of enthusiasm, plenty of commitment but no great cycling experience. I currently cycle 60-80km per day to and from work but have only completed one long ride of 140 km before."

Backstory

Britons have a chequered history in the world's greatest cycling race. At just 23 Scotsman Robert Millar won a Pyrenean stage in 1983 and in 1984 became the only native English-speaker to win the King of the Mountains title, awarded to the best climber in the race. He finished fourth overall - the best ever performance by a Briton.

Chris Boardman who won an Olympic gold medal in 1992 and broke the world hour record three times, wore the yellow jersey six times, winning the prologue - the opening time-trial stage - of the 1994 Tour with the fastest time ever recorded. Other attempts between 1995 and 1998 often started well but produced little glory. After his retirement in 1999 he said he was not able to recover from the exertion of daily racing because of a low hormone profile.

The current top Briton David Millar was tainted by a doping scandal in 2004 and was banned for two years. He returned in 2006 and is currently 76th in the 2007 Tour.

· The following correction was printed in the Guardian's Corrections and clarifications column, Friday July 27 2007. Luke Bream is not the only British rider to have completed or be completing the entire 2007 Tour de France route. The article above should have stated that he is believed to be the only one doing the entire route solo and a day in advance of the race itself. This has been corrected.